Yabla Pinyin Chart

https://chinese.yabla.com/chinese-pinyin-chart.php

Tips for Chinese Pronunciation from New Concept Chinese

https://www.newconceptmandarin.com/chinese-pronunciation/

Tingyiting (听一听）

https://tingyiting.ku.edu/

Mandarin Pronunciation

https://routledgetextbooks.com/textbooks/9781138101111/lesson1.php

Pinyin Practice and Self-Quiz–Challenge Yourself

https://pinyinpractice.com/